[gcc r12-10739] tree-optimization/116585 - SSA corruption with split_constant_offset

[Qing Zhao via Gcc-cvs]

https://gcc.gnu.org/g:8e5bd9b4b38f5b4fbd2a95d8f61168d9eeea97d3

commit r12-10739-g8e5bd9b4b38f5b4fbd2a95d8f61168d9eeea97d3
Author: Richard Biener <rguent...@suse.de>
Date:   Wed Sep 18 09:52:55 2024 +0200

    tree-optimization/116585 - SSA corruption with split_constant_offset
    
    split_constant_offset when looking through SSA defs can end up
    picking SSA leafs that are subject to abnormal coalescing.  This
    can lead to downstream consumers to insert code based on the
    result (like from dataref analysis) in places that violate constraints
    for abnormal coalescing.  It's best to not expand defs whose operands
    are subject to abnormal coalescing - and not either do something when
    a subexpression has operands like that already.
    
            PR tree-optimization/116585
            * tree-data-ref.cc (split_constant_offset_1): When either
            operand is subject to abnormal coalescing do no further
            processing.
    
            * gcc.dg/torture/pr116585.c: New testcase.
    
    (cherry picked from commit 1d0cb3b5fca69b81e69cfdb4aea0eebc1ac04750)

Diff:
---
 gcc/testsuite/gcc.dg/torture/pr116585.c | 32 ++++++++++++++++++++++++++++++++
 gcc/tree-data-ref.cc                    | 11 ++++++++---
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/pr116585.c 
b/gcc/testsuite/gcc.dg/torture/pr116585.c
new file mode 100644
index 000000000000..108c481e1043
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr116585.c
@@ -0,0 +1,32 @@
+/* { dg-do compile } */
+
+char *s1, *s2;
+extern int* my_alloc (int);
+extern int _setjmp ();
+extern void bar();
+void foo(int s1len, int s2len)
+{
+  int e;
+  e = _setjmp ();
+    {
+      int l, i;
+      int *md = my_alloc(((sizeof(int)) * (s1len + 1) * (s2len)));
+      s1len++;
+      for (; s1len; l)
+       for (; s2len; l)
+         for (; s1len; i)
+           {
+             int j = 1;
+             for (; j < s2len; j++)
+               {
+                 int cost;
+                 if (s1[1] == s2[1])
+                   cost = 0;
+                 else
+                   cost = 1;
+                 md[j * s1len ] = ((cost));
+               }
+           }
+      bar();
+    }
+}
diff --git a/gcc/tree-data-ref.cc b/gcc/tree-data-ref.cc
index 706a49f226ed..b7bca6a9d064 100644
--- a/gcc/tree-data-ref.cc
+++ b/gcc/tree-data-ref.cc
@@ -761,6 +761,14 @@ split_constant_offset_1 (tree type, tree op0, enum 
tree_code code, tree op1,
   if (INTEGRAL_TYPE_P (type) && TYPE_OVERFLOW_TRAPS (type))
     return false;
 
+  if (TREE_CODE (op0) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0))
+    return false;
+  if (op1
+      && TREE_CODE (op1) == SSA_NAME
+      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op1))
+    return false;
+
   switch (code)
     {
     case INTEGER_CST:
@@ -853,9 +861,6 @@ split_constant_offset_1 (tree type, tree op0, enum 
tree_code code, tree op1,
 
     case SSA_NAME:
       {
-       if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0))
-         return false;
-
        gimple *def_stmt = SSA_NAME_DEF_STMT (op0);
        enum tree_code subcode;